The present invention relates to a method of preparing a transmission electron microscope sample using a charged particle beam and a sample piece for a transmission electron microscope obtained as a result of the preparation method.
Conventionally, for the purpose of observing a sample with a transmission electron microscope (TEM), a sample piece for a transmission electron microscope (hereinafter, simply referred to as sample piece) is prepared using a focused ion beam (FIB, a kind of charged particle beam) system (see, for example, JP 2006-120391 A).
In a conventional sample preparation method using a focused ion beam system, a sample piece is first cut out from an original sample body with a focused ion beam, and is then grabbed by grabbing means provided to the focused ion beam system and detached from the sample body. Then, while being grabbed by the grabbing means, the sample piece is transferred to a sample holder to be fixed thereto, and is finish-processed on the sample holder such that a finished surface which can be observed with a transmission electron microscope is obtained.
In the above-mentioned sample preparation method, the focused ion beam is used not only for the purpose of processing the sample but also for the purpose of observing the sample midway through the processing. Specifically, secondary charged particles generated when the sample is irradiated with the focused ion beam are detected by a detector provided in the focused ion beam system. By converting the detected secondary charged particles into a luminance signal or the like, an image of the sample is displayed on a display portion provided to the focused ion beam system.
However, the method of preparing a transmission electron microscope sample described in Patent Document 1 has a problem in that the finished surface can not be processed with the sample piece being coupled to the sample body. Specifically, if the finished surface is processed with the sample piece being coupled to the sample body, contamination is generated on a surface of the sample piece under the influence of the charged particle beam used when the sample piece is detached from the sample body. If a sample piece with a large amount of contamination generated thereon is observed as it is with a transmission electron microscope, the quality of the observed image is adversely affected, and thus, it is difficult to process the finished surface so as to be observable with a transmission electron microscope with the sample piece being coupled to the sample body.
Therefore, in the conventional method, with the sample piece being coupled to the sample body, only rough processing as a stage before processing of forming the finished surface is carried out, and the processing of forming the finished surface is carried out after the sample piece is fixed onto the sample holder. Specifically, after the sample piece is fixed onto the sample holder, the finished surface is processed again with a charged particle beam, which decreases the productivity.
The present invention is made in view of the above-mentioned circumstance, and therefore provides a method of preparing a transmission electron microscope sample and a sample piece for a transmission electron microscope with increased productivity.